Memory devices typically include memory elements for storing data. “Flash” electrically erasable and programmable read only memories (EEPROMs) can include an electrical storage gate layer for altering a transistor threshold voltage. Thus, such devices can sense data values based on a transistor threshold voltage.
Devices having one time programmable elements, such as “anti-fuse” elements, can program an element by creating a non-reversible conductive path. Thus, such devices can sense data values based on the resistance of the cell.
Conventional conductive bridge random access memories (CBRAMs) include memory elements (sometimes referred to as programmable metallization cells (PMCs)) that are programmed and erased to different resistance levels. Many conventional CBRAM elements have a metal-insulator-metal (MIM) structure. In one state (e.g., erased), substantially no current can flow through the MIM structure. In another state (e.g., programmed), a conductive path can be formed through the insulator layer. Accordingly, such memory devices can sense data values based on a resistance of a storage element (e.g., PMC).
In all of these conventional examples, the sense operations measure a property of the memory cell that remains substantially unchanged over the duration of the operation. Other operations, typically called “write” (or program) and “erase,” are employed to change the value of the property that is to be sensed. Likewise, such conventional read operations rely on the property being sensed remaining substantially unchanged in between read operations. Changes that do occur can be considered “errors,” and additional “correction” operations can be employed to return the property of the cell to its intended value. In contrast, write and erase operations (but not read operations), a property to be sensed can change over time to establish static state to be sensed.